Gas immersion laser doping (GILD) for ultra-shallow junction formation

Abstract Gas immersion laser doping (GILD) is a very attractive technique to realize the ultra-shallow and highly doped junctions required by the International Technology Roadmap for Semiconductors (ITRS) for future CMOS technologies. In the present work, gaseous dopant precursors (BCl 3 ) are chemisorbed on the Si surface, and partially incorporated during the melting/recrystallisation of the Si top layer induced by an UV laser pulse ( λ =308 nm, pulse duration ≈25 ns). The resulting thickness and dopant concentration of the doped layer depend on the laser energy density and the number of chemisorption/laser-induced incorporation cycles (up to 200). GILD processed junctions are box-like and exhibit depths ranging from 14 nm to 65 nm, with sheet resistances ranging from ≈110 to 20 Ω/□ (respectively), dopant concentrations well above the B solubility limit in Si (up to 3×10 21 at/cm 3 ) at local thermodynamic equilibrium (LTE) and abruptness of 5–2 nm/decade. Moreover, in situ optical characterization shows the GILD technique capabilities to realize the sub-10 nm thick shallow junctions needed for the sub-40 nm node ITRS predictions.